This invention relates to the recovery of hydrocarbons from oil-bearing deposits of limestone and dolomite and is particularly concerned with an in situ recovery process which permits the recovery of hydrocarbon liquids in substantial quantities.
A large amount of oil exists today in the United States trapped in deposits of limestone located throughout the country. The current shortage of oil has made it highly desirable to recover the liquid hydro-carbons from these deposits. It has been suggested that conventional methods of steam stimulation used in the past with success in recovering oil from tight formations of sand be applied in an attempt to recover heavy oil from limestone deposits. Such methods normally include drilling a series of several boreholes into the formation around a central borehole and injecting high pressure steam into the central borehole. The heat from the steam moves by conduction and convection outward from the central borehole decreasing the viscosity of the trapped oil and forcing it toward the other bore-holes from which it is eventually recovered. Attempts to apply such methods for recovering the oil from limestone deposits in Southwest Texas, however, have proven ineffective evidently because the viscosity of the oil is so great and the permeability of the formations so low that it is impossible to force the oil or the steam through the limestone. Thus, at this time, there appears to be no commercially feasible process for the in situ recovery of heavy oil from such limestone deposits.